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Lead Production from High-grade Galena Concentrates by Ferric Chloride Leaching and Molten-salt Electrolysis.

The U.S. Bureau of Mines investigated an alternative process to smelting for the production of lead metal. The process eliminates sulfur dioxide generation and minimizes particulate lead emissions. The process involves ferric chloride leaching of galena concentrate to produce lead chloride, followed by molten-salt electrolysis of the lead chloride to yield lead metal and chlorine. The chlorine is used to regenerate ferric chloride in the leaching solution. The process was tested on both a bench scale and a larger scale which had a capacity of 225 kg of lead metal per day. The large-scale leaching and electrolysis tests were performed in three 10-day and six 5-day campaigns, during a period spanning 28 mo. The study was carried out using a southeastern Missouri lead concentrate. Typical lead recovery was 98 pct. Process problems related to impurity buildup and control were studied. When copper and silver impurities were removed from the leaching solution, lead metal purity increased to 99.999 pct. Lead-in-air levels and lead-in-blood levels of operating personnel were monitored. Large-scale electrolysis tests were performed in a 3,000-a cell with horizontal, flat-plate electrodes. Electrolysis proved to be the most expensive step in the process because the energy requirement in the large cell was 1.32 Kw.H/kg. Subsequently, the cell was operated with a more efficient electrode design, and the energy requirement was decreased to 0.66 Kw.H/kg.